The long term goal is the development of an all in the ear signal processing hearing aid. The design of the hearing aid would incorporate the following novel features: 1. Feedback and level control will be achieved by a probe microphone placed within the proximal end of the hearing aid earmold to accurately determine the actual sound pressure level at the ear drum. 2. The input signal will be amplified in individual 1/3 octave frequency bands. Amplification will be limited to a subject's loudness discomfort level as determined by separate testing for each individual. 3. Amplification will be done selectively based on the behavior of the input signal. Amplification activication can be based on a combination of absolute level, change in level, average change in level over a given time period, the number of zero crossings over a given time period or other time domain functions. The most appropriate amplification activation function will be determined through testing. The goal of the first six months of the project will be to breadboard a working model o the processor using available off shelf components. This will result in a cigar box sized processor which can be connected to an existing ear mold transducer for testing. The initial performance will be measured using a Kemar mannequin. Initial process control will be by means of a microcomputer.